[Pearl mussels of the genus Dahurinaia (Bivalvia, Margaritiferidae): differently sized groups of Margaritifera dahurica Middendorff, 1850].

Molecularand genetic studies have revealed that all five species of pearl mussels of the Dahurinaia genus (Bivalvia, Margaritiferidae) inhabiting the upper basin of the Amur River on the territory of Transbaikalia belong to one species Margaritifera dahurica Middendorff, 1850. Based on the statistical analysis, it has been shown that morphometric shell ratios form continuous variation series without differentiation on discrete groups. It has been found that changes in these ratios are caused by the shell growth of pearl mussels and their morphological variations reflects the high level of polymorphism, Comparator species of the genus Dahurinaia are differently sized groups of one polymorphic biological species M. dahurica.